Improvements towards a reliable fabrication process for cMUT

This paper reports the fabrication process for capacitive micromachined ultrasonic transducers (cMUT) using surface micromachining techniques. We describe the processing steps that allow control with high repeatability of the transducer geometrical features (membrane radius, membrane thickness, vert...

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Bibliographic Details
Published in:Microelectronic engineering 2003-06, Vol.67, p.602-608
Main Authors: Cianci, E., Visigalli, L., Foglietti, V., Caliano, G., Pappalardo, M.
Format: Article
Language:English
Subjects:
Applied sciences
Capacitive transducer
Electronics
Exact sciences and technology
Microelectronic fabrication (materials and surfaces technology)
Operation in liquid
Sealed cavities
Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
Surface micromachining
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Summary:This paper reports the fabrication process for capacitive micromachined ultrasonic transducers (cMUT) using surface micromachining techniques. We describe the processing steps that allow control with high repeatability of the transducer geometrical features (membrane radius, membrane thickness, vertical distance between electrodes) and of the mechanical properties of the structural materials (stress in the silicon nitride layer). The transducers are fabricated with the fixed electrode patterned on top of the silicon wafer, which works as a support for the device, thus reducing parasitic capacitances. Tests of cMUTs with 0.5-μm-thick silicon nitride membranes suspended on 0.4-μm-thick cavities were performed showing resonance frequency at 5.5 MHz.
ISSN:0167-9317
1873-5568
DOI:10.1016/S0167-9317(03)00120-5